Funds are requested to study the specific functions of the Crisp-1 protein. Crisp-1 is produced in the epididymis and associates with the sperm during transit through the organ. The high similarity to a known ryanodine receptor agonist suggests that Crisp-1 may have a role in ion channel regulation. Changes in calcium concentrations are required for sperm to become capacitated and undergo the acrosome reaction in preparation for fertilization. In vitro capacitation studies of rat sperm show that when Crisp-1 is present, sperm are prohibited from capacitating. The specific aims focus on determining the mechanisms involved in the inhibition of capacitation by Crisp-l, identification of the receptor for Crisp-1 on sperm, identification of the Crisp-1 active site, and investigation of the ability of other members of the Crisp family to mimic the actions of Crisp-1. Crisp-1 will also be tested for its ability to inhibit capacitation and the acrosome reaction in human sperm. Finally, potential actions of Crisp-1 on the egg, such as the ability to regulate cortical granule fusion, will be examined. The proposed studies will provide significant contributions to our understanding of sperm function and may also have potential application to male infertility and contraceptive development.